A device in which a rotatable friction roller comprising several cylindrical rotation elements arranged in a row on a common driving shaft is used to wind up yarns on a rotatable tube is known from EP 0063 690 A1. One of these rotation elements is attached fixedly on a shaft so that the friction roller is driven. The tube or bobbin which is in contact with this friction roller presses against the rotatable friction roller and is driven by the latter. To be able to also drive conical tubes or bobbins, the friction roller is provided with a differential gear thanks to which the friction roller has different circumferential speeds at its two ends to drive the bobbin. To drive the friction roller, its central area is firmly attached to the drive shaft. The two outer portions of the friction roller are rotatable in relation to the drive shaft.
A similar friction roller is known from DE 34 46 259 C2. With this device, the part which is firmly connected to the drive shaft is provided with a cover which is freely rotatable in relation to the drive shaft.
DE 36 16 406 A1 discloses another device where the toothed wheel rotating together with the drive shaft is a bevel wheel which meshes with corresponding toothed wheels of the two rotatable elements. Labyrinths are used to prevent yarns or dirt from infiltrating between the rotatable elements.
DE 38 23 403 discloses the utilization of friction gearing whereby the axes of the friction wheels are parallel to the axis of the winding roller. This device has the disadvantage that in particular its friction wheel gearing is delicate and cannot bear much load. Only friction wheels with relatively small diameter can be used here. Sufficient pressure between friction wheel and running surface is not ensured.
CS 261 950 B1 discloses a winding device for conical bobbins with a differential gear in which the transmission of force is effected by means of friction. A ring which rotates with the drive shaft is attached to the latter for this purpose. This ring is provided with recesses in which balls are inserted. The friction surfaces of the rotation elements lie axially against the latter. A spring exerts axial force upon the bearing which can be shifted in relation to the drive shaft so that one rotation element is connected interlockingly via the balls to the other rotation element. The disadvantage of such a friction drive is the fact that it has great internal friction. Another disadvantage is the fact that constant translation ratios are not ensured. Only a point-shaped contact exists between the contact surfaces. Due to the limitation of the space into which the balls are inserted in the radial direction, only relatively small balls can be used, and this further worsens the drive conditions.
A winding device with toothed wheel differential gearing where the rotational elements are also mounted so as to be capable of axial shifting is known from DE-A 40 40 650. The disadvantages of this device are that it is very expensive. The axial shiftability contributes to the fact that gears or bearing locations can no longer be sealed off sufficiently from their environment. The winding device must be stopped for cleaning, since toothed-wheel gear transmissions make it impossible to stop one of the rotation elements during operation. This involves the danger that gears of the rotation element would be destroyed due to the high rotational speeds.
In known winding devices, meshing teeth are usually used for the transmission of the movement. These have however the disadvantage that they are expensive and delicate, that a precise adjustment of the winding roller is required and that they are not suitable for higher rotational speed. Higher rotational speeds occur especially when part of the winding roller is stopped by hand, for example, in an attempt to remove dirt, e.g. yarns, from the gap between the parts of the winding roller into which they may have been pulled. In such a case, the gears are subjected to high loads which could lead to a destruction of toothed-wheel gear transmissions. The friction gear transmissions known in the state of the art are also not suitable in practical use because of the disadvantages described above.
It is a further disadvantage of the known winding devices that they can be put out of commission by dirt, e.g. yarns pulled into the devices. Blockage of the gear transmission, e.g. by yarns, as well as due to the jamming of yarns in the gaps between the parts of the friction roller, causes the transmission function to be interrupted so that the entire friction roller rotates over its entire length at the same circumferential speed. It is another disadvantage of the known devices that the driving shaft must be stopped to be cleaned so that access is afforded in the area of the gear transmission or between two parts of the friction roller, for example. Furthermore the friction rollers must be disassembled at least in part for maintenance, which is time consuming. This causes long stoppage times of the machine with the winding devices according to the state of the art.